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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

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paraffin wax, ceresine and beeswax being followed according to the type
of candle examined.                                                                      ^

For the quantitative, determinations it is well to melt a whole candle
or at least various pieces taken from several candles at different points in
order to obtain a homogeneous and representative sample.

It is further necessary to determine the weight of the wick, several
pieces being broken from one or more candles and weighed and the wick
then carefully separated and weighed : the weight of the wick is referred
to 100 parts of candle.

The commonest cases of analysis of candles are the following:

10 grams of the sample are heated and shaken with 50 c.c. of 90% alcohol
on the water-bath, the liquid being subsequently titrated withdecinormal
potassium hydroxide in presence of phenolphthalein : i c.c. N/io-KOH =
0-027 gram of stearinc (mean molecular weight of ordinary stearine = 270).

The liquid is then again heated on the water-bath for about an hour,
with frequent shaking, with 4-5 c.c. of concentrated potassium hydroxide
solution to saponify the small quantity of neutral fat or .any lactones present
in the stearine (for greater precision the saponification number also may
be determined). The solution is then diluted with water and allowed to
cool until the paraffin is thoroughly solidified to a solid disc, the aqueous
liquid being then decanted off and the paraffin washed several times with
water, being heated and cooled each time. The washed paraffin is finally
collected into a. dish, dried in an oven at 105 and weighed.

The paraffin thus separated is then tested for ceresine by the methods
given on p. 364.

The stearic acid (stearine) calculated from the acid number and the
paraffin weighed directly are then referred to 100 parts of candle, allowance
being made for the weight of the wick (see example given below for case 6).

For rapid, approximate, determinations it is sufficient to calculate the
stearic acid from the acid number and the paraffin by difference.

it may be necessary to calculate either all three of the components or only
the paraffin (or ceresine).

i. Determination of all of the components. The acid and saponification
numbers are determined in the usual way, the various components being
then calculated as in the following example.

EXAMPLE : The wick of a candle is found to represent 0-4% of the weight
of the candle, while the wick-free mass has:

Acid number = 77-0
Saponification         ,,    = 84-7,
so that

Ester number =  7-7.

Assuming the mean ester number of wax to be 75, the mean saponification
number of wax to be 95 and the mea,n saponification number of stearic acid
to be 207, the various components are calculated as follows:

(a) The wax (x) is given by the ester number,

75 :100 :: 7-7 : n,


x = 10-26% of wax.uctions laid down in the articles on stearine, This is the method proposed by the Committee for the analysis of degras at the